Metal cans are a common form of packaging for food and beverage that offer numerous advantages when compared to other material packaging forms, including metal's ability to be hermetically sealed for long storage, its low cost, and its excellent recyclability. “Easy opening” metal food containers which, for purposes of this disclosure include opening systems that do not require a separate can opening tool to access the contents, offer even greater consumer convenience for many packaged products. Two common systems for providing easy opening functionality are “Stay on Tab” (SOT) systems and peel-seam systems.
SOT easy opening systems, such as those described in U.S. Pat. No. 3,731,836, score a line in the container end panel to outline a weakened opening area and use the leverage of a rivet-retained tab to take advantage of the weakened score line to push the opening area through the end panel. As the name suggests, the tab remains affixed to the end panel after opening.
Partial aperture pour openings in beverage containers are well known in the art. In some instances, the score line does not create a fully contiguous opening within the end of the panel so that, after the opening is pushed through the end panel, the area within the scored line remains connected to the end panel.
The SOT was an improvement over earlier forms of easy opening end panel systems such as those described in U.S. Pat. No. 3,664,543 wherein the scored tab was completely removable from the end panel and often discarded indiscriminately, thereby creating consumer safety and litter problems. Thus, it is well recognized that loose tabs are not acceptable to consumers in easy opening container end panels.
In some cases, SOT design principles have also been extended to produce full aperture easy opening ends for metal food cans and other containers. In these applications, the score line is now fully contiguous around the removable end panel to which the tab lever is joined.
Although there have been improvements to SOT container ends, there are some inherent disadvantages to scored openings that are forced open through the lever action of a tab. For example, it can be difficult to access and grip the tab, often resulting in broken finger nails or injury to a fingertip, and it can be difficult for a consumer to less than optimal ease of opening as the tab can be difficult for consumers. Even when the tab can be accessed, the force required to initiate the opening of the can and release the pressure inside the can is often too great for many consumers to apply. If the consumer is able to open the can, they are then exposed to the sharp edges inherent to the score line break, and, to top it off, these type of opening systems do not lend themselves to reclosing since the score line break deforms the freed panel in a way that is not readily reversed.
Peel-seam systems as exemplified by U.S. Pat. No. 5,752,614 can also be used for easy-opening closures on hermetically sealed containers. A bounded aperture, often in the form of a flattened circular rim, is covered by a membrane typically comprised of a tear-resistant metal foil/polymer laminate that extends over the opening and its periphery. The container is sealed by a continuous loop of food safe adhesive applied between the overlapping edges of the membrane and the container wall. The adhesive is selected to give a bond with sufficient shear and tensile strength to hold up in filling, processing, and storage conditions, yet a low enough peel strength to enable easy-opening of the container.
Directional pull by a consumer on an edge tab of the membrane stresses the adhesive bond in peel mode, and continuing this motion progressively overcomes the total bonding force of the adhesive around the full perimeter. However the detached membrane loses its adhesive character and curls and distorts and is not a useful structure for reclosing.
There is a need, therefore, for a container opening system with a tab or lever that is easy to access and grip and that, when used in connection with pressurized containers, does not require inordinate force to release the pressure inside the container. In addition, there is a need for a container that provides the convenience to consumers of reduced spillage or contamination of contents after the container has been opened. The need extends to a container opening system that, once opened, does not expose the user to sharp edges around the aperture and further allows reclosing of the container in a way that is readily reversed.